(a) Technical Field
The present disclosure relates to a system and a method for learning a transferring torque for a hybrid vehicle, capable of improving drivability and mileage by learning a transferring torque of an engine clutch.
(b) Description of the Related Art
Generally, a hybrid vehicle has benefits of improving mileage of a vehicle and satisfying more rigorous On-Board Diagnostics (OBD) regulations with respect to exhaust gas of a vehicle.
One or more of a motor and an engine are provided in the hybrid vehicle, which includes a battery for storing power of a high voltage for driving the motor, an inverter for converting direct voltage from the battery into alternate voltage, and an engine clutch arranged between the engine and the motor to transfer power from the engine to a driving shaft.
The hybrid vehicle is configured to operate in a hybrid electric vehicle (HEV) mode or an electric vehicle (EV) mode by coupling or decoupling an engine clutch in accordance with acceleration/de-acceleration, which is determined by driver operation of an acceleration pedal and a brake pedal, load, a velocity of the vehicle, a state of charging a battery (SOC), etc.
When a hybrid vehicle converts into a HEV mode from an EV mode, the engine clutch is coupled after the velocities of the engine and the motor are synchronized, so as not to produce torque variation in a course of transferring power between the engine and the motor of different power sources, thereby ensuring drivability of a vehicle.
However, in a case of keeping a battery at a low state of charging (LOW SOC), under the conditions that the temperatures of the battery and the motor exceed set standard temperature conditions, and a gradient of a road on which a vehicle is driving has a steep slope surface, etc., there arises a case where the vehicle has to start by slip-controlling the engine clutch. In particular, precise pressure control is required in order to slip-control the engine clutch under the driving conditions as described above.
A transferring torque of the engine clutch refers to a torque transferred with friction surfaces to which both ends of the engine clutch are in contact physically (i.e., a load applied to both ends of the engine clutch), which can be estimated basically through an effective pressure and a frictional coefficient.
In a starting operation of a hybrid vehicle, a control of an engine clutch is an important parameter that influences drivability and mileage; however, there occur characteristic deviations that influence the control of the engine clutch, such as: the variations of the current and pressure of a solenoid valve for operating the engine clutch, deterioration of the solenoid valve, and variation of the frictional coefficient due to deterioration of frictional materials disposed on both ends of the engine clutch.
As described above, there occur characteristic deviations in the hybrid vehicle in accordance with durability of the components related to the control of the engine clutch, and thereby not controlling precisely the engine clutch can worsen the drivability and mileage.
A conventional hybrid vehicle does not incorporate technology for learning a transferring torque of the engine clutch, and thus there may occur characteristic deviations per kind of vehicle with respect to estimating the transferring torque. Accordingly, differences of the starting acceleration velocity may occur in a control of the engine clutch for the starting acceleration per kind of vehicle and in accordance with durability.
Further, the elements that are feed-forwarded to the engine controller in a control of the engine clutch for the starting acceleration are not accurate, and thus control of an engine velocity may not respond optimally to the starting acceleration. Accordingly, a technology for estimating more precisely a transferring torque through a clutch has been required.
The description provided above as a related art of the present invention is just for helping understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.